manufacturers. When the torque values are included in
a technical manual, these values take precedence over
When you are using a drive-end extension, the
the standard torque values provided in the Structural
torque wrench reading must be computed using the
Hardware Technical Manual, NAVAIR 01-1A-8.
formula in figure 3-44:
Separate torque tables and torquing considerations
are provided in NAVAIR 01-1A-8 for the large variety
of nuts, bolts, and screws used in aircraft construction.
You should use this manual when specific torque values
are not provided as a part of the removal/replacement
Figure 3-44.--Drive-end extension formula.
To obtain values in foot-pounds, divide inch-pound
values by 12. Do not lubricate nuts or bolts except for
corrosion-resistant steel parts or where specifically
S = handle setting or reading
instructed to do so. Always tighten by rotating the nut
first if possible. When space considerations make it
T = torque applied at end of adapter
necessary to tighten the fastener by rotating the bolt
La = length of handle in inches
head, approach the high side of the indicated torque
range. Do not exceed the maximum allowable torque
Ea = length of extension in inches
value. Maximum torque ranges should be used only
If you desire to exert 100 inch-pounds at the end of
when materials and surfaces being joined are of
the wrench and extension, when La equals 12 inches
sufficient thickness, area, and strength to resist
and Ea equals 6 inches, it is possible to determine the
breaking, warping, or other damage.
handle setting by making the calculation shown in
For corrosion-resisting steel nuts, use the torque
values given for shear-type nuts. The use of any type of
drive-end extension on a torque wrench changes the
dial reading required to obtain the actual values
indicated in the torque range tables. See figure 3-43.
Figure 3-45.--Sample calculation.
Whenever possible, attach the extension in line
with the torque wrench. When it is necessary to attach
the extension at an angle to the torque wrench, the
effective length of the assembly will be La + Ea, as
shown in figure 3-43. In this instance, length Eb must
be substituted for length Ea in the formula.
NOTE: It is not advisable to use a handle extension
on a flexible beam-type torque wrench at any time. The
use of a drive-end extension on any type of torque
wrench makes use of the formula necessary. When the
formula has been used, force must be applied to the
handle of the torque wrench at the point from which the
measurements were taken. If this is not done, the torque
obtained will be in error.
Figure 3-43.--Torque wrenches.